Drying refractory linings of furnaces



Jan. 19, 1954 P. BLANCHARD 6,

' DRYING REFRACTORY LININGS OF FURNACES Filed March 23, 1951 16 v 15 I M I I ll 7!! III! Patented Jan. 19, 1954 DRYING REFRACTORY LININ GS F FURNACES Paul Blanchard, Paris, France Application March 23, 1951, Serial No. 217,083

Claims priority, application France May 5, 1950 2 Claims. (01. 34 4'z) Many furnaces and metallurgical devices are provided with an internal refractory lining made up wholly or partly of raw products such as silicaceous earths. Theyare generally formed of grains of silica or quartzites most frequently fused together with-a refractory clay used in a relatively small proportion so as not to appreciably lower the fusion or softening point under load of the silicaceous substance.

Those coatings are generally formed by packing the earth between a removable sheet metal mandrel which determines the internal shape of the furnace and the external sheet metal casing of the device, that casing being, if desired, previously internally provided with refractory or heat resisting brickwork of a more permanent or more durable character than the earth.

After the earth coating ha become more or less Worn, as a result of the utilisation of the apparatus, what remains of the earth is out out or destroyed and a new sleeving or" the linin is 2 zone of rapid wear and a reduction in the rate of wear of the linings as a whole. the linings was doubled.

The object of the present invention is therefore first of all a method of drying refractory linings of industrial furnaces and, the like, consisting inregulating the heating of the linings to be dried so as not to exceed a predetermined pressure (for example, 50 grams per mm?) at any point in the lining.

I have noted that between the ambient temperature and 90 no pressure was detected in the lining, and that it is only between 90 and 100 that The present invention therefore has as an object a method of drying refractory linings of industrial furnaces and the like consisting in carrying the temperature of the lining rapidly to a temperature below a 90 C. and continuing the drying so that a predeagain effected as described above. As the earth is fused together by first of all moistening it to an extent depending upon its clay content, the lining as a whole must be completely'dried before the apparatus can be put into service. That drying is normally effected by means of a wood fire.

which is lit at the lower end of the apparatus and is first of all made to burn slowly and then more rapidly and is then replaced by a coke lire.

As the lining, if it is properly packed, is of small'permeability, the moisture is evolved with great difficulty and the vapour which is formed leads to substantial local pressures in the joints inthe lining. If the drying is carried out rapidly, flaking or cracking of the lining takes place be fore the latter is put to use, and the life of the lining is therefore considerably reduced. If the drying is carried out more slowly, no cracks appear and the user has the impression that the operation has been properly carried out.-

I In general, that'is not so. I have noted that linings 40 cm. thick'of rotary furnaces which appeared to have been very properly dried, showed 'on use first of all relatively slow wear over a thickness or about 10 cm. and then much more rapid wear of from 10-30 cm. and. finally a slower rateof wear at the end. I therefore had the idea of checking the pressures developed at different points inthe lining during the, drying. I have noted that if the pressures are relatively small (about lilo-150 grams per mm?) in the parts in which the wear is slow, they commonly reach 300-400 grams and even more in the parts inwhich the wear is rapid.

By means of a precisely adjustable gas burner, the dryings were therefore carried out methodically so that a pressure of grams per mm? was never exceeded at the points at which the check was made. The result was the displacement of the termined pressure is not exceeded at any point in the lining.

Furthermore, I have noted that the vapour produced in the lining during the drying is displaced towards the inside'which is heated towards the external wall where condensation of the vapour takes place. It is therefore advantageous to heat the outside also to an extent suihcient to avoid such condensation, but the external heating must not be so violent as'to cause the pressure to rise. Now such pressure can be avoided with certainty if the heating does not exceed 90. Consequently, the present invention has as an object a method of drying refractory linings of industrial furnaces and the like consisting in heating the external wall of the furnace preferably to a tern-V perature lower than 90 at any rate at the beginning of the drying.

When the drying has been partly effected, the

4 temperature can be raised above 90 without the production of pressure within the lining.

Finally, I have noted that, other things being equal, a rapid rise in temperature ofthe lining,

either continuous or spasmodic, causes pressure to be produced which wasnot produced when the rise in temperature was'slower. According to the present invention, the drying of the refractory linings of industrial furnaces and the like is effected by causing the temperature to change slowly and very regularly.

It should benoted that if the external wall is heated for example to the risein tempera ture of the, internal lining can be accelerated,

there being no risk that thevapour will condense and the difference of temperature between two neighbouring points in the lining being, other things being equal, smaller..

As the heating means which are used nowadays do not allow'a suihcientlyhigh regularity to be obtained, sufficiently accurate means for control- The life of v ling the temperature must be used as must means for evening, out the irregularities of operation of the source of heat.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of speciiic embodiments when read in connection with the accompanying drawings, in which: i

Fig. 1 is an elevational sectional view of a drying installation for refractory linings of moveable industrial furnaces;

Fig. 2 is an elevational sectional view of a modified drying installation for immovable furnaces; and

Fig. 3 is a cross sectional view of Fig. 2 along line III-III,

In the case of the diagram of Fig. l, the furnace i4 is introduced into a drier l5 and put intocommunication a furnace i, the hot gases of which are adjusted to a temperature which is maintained constant or variable at will with a sufficient degree of precision. For example, a gas or fuel oil burner 2 can be used together with a'fan 3 blowing an extra quantity of air the amount of which is controlled by a damper 4 controlled by a regulator 5 which is itself controlled by a pyrometer rod 6 which is surrounded by the hot gas within the furnace M. The quantity of air supplied to the burner 2 could also have been varied by regulation of the openings of the fan or of a damper disposed at exit from or entry to the fan. In both cases, the slight possible variation in delivery of the burner 2 are thus automatically corrected by the action of the regulator 5. The hot gases escape to the upper part of the furnace Hi and can be diluted in a mass of air, of gas or of smoke also blown by the same fan 3 through the duct it. They are taken along by the fan at the base of the drier 5 through the duct H and distributed towards the exit from the combustion chamber of the burner through the duct l3 and towards the upper part of the drier it where they dilute the hot gases leaving the furnace.

At the beginning of the drying the temperature in the furnace I4 is limited to the neighbourhood of 1G0? The annular chamber lil formed by the furnace is and the drier It rises progressively in temperature. When it tends to exceed a temperature of 90 detected by the pyrorneter 8 which acts on the regulator 9, the baffle it which is motorised starts to open and the fan 3 sucks in cold air at the same time as the atmosphere from the annular chamber I3 which brings the temperature of the latter back to 90.

By acting on the regulator 5, either manually or automatically, the temperature in the furnace is caused to rise progressively. Similarly, and from time to time, the sup ly to the burner 2 is increa ed. could be regulated by an automatic device following a course predetermined from a precisely determined curve of the rise in temperature within the furnace, takin into account the characteristics of the lining (tightne s of packing, moisture conte t, permeabilitv of the earth used. etc).

Towards the end of thedrying, the regulator 9 is actuated so as to cause the temperature in the chamber !8 to r se slightly in order to ensure complete desiccation of the refractory lining. A flue Clearly, the supply to the burner 4 l l ensures evacuation of the excess gas supplied to the circuit by the burner 2.v To the same end, an extra outlet l2 can be provided.

In the diagrams of Fig. 2 and Fig. 3 the reference numerals used to designate the various elements of the installation of Fig. 2 are the same as those serving to designate the corresponding elements of Fig. 1 except that in Figs. 2 and 3 the numerals are primed. The drier 15 of Fig. 1 is replaced in F g. 2 by a double wall 15 mounted round the fixed furnace I4.

I claim:

1. An arrangement for drying the refractory lining of an industrial furnace comprising, in combination, a casing adapted to enclose a furnace to be treated and having an inner surface adapted to be spaced from said furnace; a source of heat; first conduit means communicating with said source of heat and adapted to supply heated air to the interior of the furnace; second conduit means communicating with said source of heat on one end and with the interior of said casing at the other end so as to conduct heated air to the outside of the furnace; blower means communicating at the suction side thereof with the interior of said easing'and at the pressure side thereof with said second conduit means intermediate said source of. heat and said casing: Outlet means in said casing adapted tocommunicate with the atmosphere; damper means, located in said second condu t means between said blower means and said source of heat;- and temperature sensitive means controlling said damper means so as to regulate the amount of gases passing through said damper and to said source of heat.

An arrangement for drying a refractory lining on the inner surface of a furnace, comprising, in combination, a casing adapted to enclose a furnace to be treated and to be located at a spaced distance from said furnace so as to form a space between the inner face of said casing and the outer surface of said furnace; a source of heat; first conduit means communicating with said source of heat and with the interior of said furnace for conducting heated gases from said source of heat to the interior of said furnace; second conduit means communicating with said sourceof heat and with said space between the outer surface of said furnace and the inner face of said casing for conductingheated gases from said source of heat to'the exterior of said furnace within said casing; and temperature control means operatively connected to said second conduit means for controlling the temperature of the gases conducted to the exterior of said furnace so as to be lower than the temperature of the ases conducted to the interior of said furnace.

PAUL BLANCHARD.

References Cited in the file of this patent UNITED STATES PATENTS Number 

